Volatile Compounds in Honey: A Review on Their Involvement in Aroma, Botanical Origin Determination and Potential Biomedical Activities

Volatile organic compounds (VOCs) in honey are obtained from diverse biosynthetic pathways and extracted by using various methods associated with varying degrees of selectivity and effectiveness. These compounds are grouped into chemical categories such as aldehyde, ketone, acid, alcohol, hydrocarbon, norisoprenoids, terpenes and benzene compounds and their derivatives, furan and pyran derivatives. They represent a fingerprint of a specific honey and therefore could be used to differentiate between monofloral honeys from different floral sources, thus providing valuable information concerning the honey’s botanical and geographical origin. However, only plant derived compounds and their metabolites (terpenes, norisoprenoids and benzene compounds and their derivatives) must be employed to discriminate among floral origins of honey. Notwithstanding, many authors have reported different floral markers for honey of the same floral origin, consequently sensory analysis, in conjunction with analysis of VOCs could help to clear this ambiguity. Furthermore, VOCs influence honey’s aroma described as sweet, citrus, floral, almond, rancid, etc. Clearly, the contribution of a volatile compound to honey aroma is determined by its odor activity value. Elucidation of the aroma compounds along with floral origins of a particular honey can help to standardize its quality and avoid fraudulent labeling of the product. Although only present in low concentrations, VOCS could contribute to biomedical activities of honey, especially the antioxidant effect due to their natural radical scavenging potential

Inferential non‐centred principal curve analysis of time‐intensity curves in sensory analysis: the methodology and its application to beer astringency evaluation

Improving technologies and better understanding of sensory phenomena have lead sensory analysts to develop statistical methods to assess sensations that endure over time (e.g. the bitterness or astringency of a beer) dynamically. The data produced by this type of experiment is classically a time‐intensity (TI) curve, and their analysis remains an active research topic. The classical approach, widely used in this context, starts by extracting some significant parameters from the initial curves (maximum intensity, area under the curve (AUC), etc.). Descriptive data analysis or statistical modelling is then applied to get information from these summary parameters. This paper presents a different method, called inferential non‐centred principal curve analysis (INCPCA), for the analysis of TI curves. It combines multivariate analysis (to visualise the curves in a space of smaller dimensions) with statistical modelling (aimed at enhancing the significance of factor effects). Non‐centred principal curves (NCPCs) are first extracted from the curves matrix. They decompose the TI curves into different interpretable components. Score plots are used to represent the projection of the initial curves in the space of the first principal curves and allow factors and judge effects to be visualised. Mixed modelling is then applied to test the significance of these effects using PCA scores as model responses. The classical and INCPCA methods are illustrated on a TI experiment exploring the relation between beer astringency and three factors of interest: pH, O2 content and aging. Eight beers arranged in a 23 factorial design were tested in triplicate by eight trained judges

Optimized extraction procedure for quantifying norisoprenoids in honey and honey food products.

Norisoprenoids appear as promising compounds for authenticating unifloral honeys. So far, however, no method has been optimized for their isolation from a matrix so rich in sugars. In this framework, an original extraction procedure based on the use of Amberlite XAD-16 was developed. Recovery factors were determined and compared with those obtained with another resin (XAD-2). This was done for different model media and various norisoprenoids. In aqueous or alcoholic solutions, the efficiency of both resins proved very high. As expected, addition of honey decreased the adsorption of nonpolar compounds. This effect was much more pronounced with the lower-porosity XAD-2 support. Sugar addition markedly improved the recovery factors obtained with the XAD-16 resin in the case of more polar norisoprenoids

Floral quality and discrimination of Lavandula stoechas, Lavandula angustifolia, and Lavandula angustifolia x Latifolia honeys

Portuguese lavender honeys are generated from the nectar of Lavandula stoechas, whereas French lavender honeys are exclusively derived from Lavandula angustifolia, Lavandula latifolia, or hybrids of these two species. In the framework of the floral origin authentication of such honeys, volatile compounds from L. stoechas, L. angustifolia, and L. angustifolia x latifolia unifloral honeys were investigated. The aromatic profiles of French and Portuguese lavender honey samples showed major qualitative and quantitative differences, but no volatile compound is characteristic of L. stoechas honeys only. As expected, n-hexanal, n-heptanal, phenylacetaldehyde, and n-hexanol, previously proposed to authenticate French lavender honeys, were found at concentrations far above the published discrimination thresholds. Coumarin, previously proposed to characterize French lavender honeys, emerges here rather as an indicator of the freshness of lavender honey, being mainly released from glycosides during storage. Lastly, L. angustifolia honeys were distinguishable from hybrid-derived samples by their lower phenylacetaldehyde and higher heptanoic acid content. (C) 2002 Elsevier Science Ltd. All rights reserved

Assessment of added glutathione in yeast propagations, wort fermentations, and beer storage

Glutathione (GSH) is one of the most abundant low-molecular-weight thiols found in living cells. Concentrations varying from 8 to 37 nmol/mg of cells were measured in brewing yeast. While other studies emphasize the key role of GSH in the response of some genetically modified yeasts to different stresses, our results show that GSH added to the yeast propagation medium has no significant impact on the growth of most brewing yeast strains. In high-gravity primary fermentations, a slight positive effect was observed during the first week with only two (lager) yeast strains. Added to phosphate buffer or beer, GSH imparts a reducing activity similar to that of ascorbic acid, but it proves to be a much less powerful antioxidant than phenolic compounds. Whatever the chosen step for spiking, beers aged in the presence of GSH were characterized by strong sulfurous off-flavors, despite a mere 6% degradation of the tripeptide

Beer astringency assessed by time-intensity and quantitative descriptive analysis: Influence of pH and accelerated aging

pH and oxygen are usually considered as the main factors influencing the organoleptic stability of beer. Polyphenols from malt and hop contribute to several characteristics of beer flavor, but their incidence on astringency is rarely mentioned. In this work, effects of pH (3.0 and 5.0) and accelerated aging (0 or 5 days at 40 degrees C with low or high level of oxygen in the bottle) on astringency were measured by two sensory analysis methods: quantitative descriptive analysis and time-intensity analysis. In addition, the polymerization degree of polyphenols was determined for the different samples in this study. Whatever the sensory technique used, a trained panel showing high repeatability identified pH as the only factor having a significant effect on astringency. Accelerated aging, even with high level of oxygen in the bottle, does not significantly modify perception of this sensation compared with the 4 degrees C-stored beer, probably because the variation of polymerization degree of polyphenols was not sufficient to be detected by the panelists. (C) 2005 Elsevier Ltd. All rights reserved

Sensory analysis applied to honey: state of the art

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Evaluation of beer deterioration by gas chromatography-mass spectrometry/multivariate analysis: a rapid tool for assessing beer composition

Beer stability is a major concern for the brewing industry, as beer characteristics may be subject to significant changes during storage. This paper describes a novel non-targeted methodology for monitoring the chemical changes occurring in a lager beer exposed to accelerated aging (induced by thermal treatment: 18 days at 45 ◦C), using gas chromatography–mass spectrometry in tandem with multivariate analysis (GC–MS/MVA). Optimization of the chromatographic run was performed, achieving a threefold reduction of the chromatographic time. Although losing optimum resolution, rapid GC runs showed similar chromatographic profiles and semi-quantitative ability to characterize volatile compounds. To evaluate the variations on the global volatile signature (chromatographic profile and m/z pattern of fragmentation in each scan) of beer during thermal deterioration, a non-supervised multivariate analysis method, Principal Component Analysis (PCA), was applied to the GC–MS data. This methodology allowed not only the rapid identification of the degree of deterioration affecting beer, but also the identification of specific compounds of relevance to the thermal deterioration process of beer, both well established markers such as 5-hydroxymethylfufural (5-HMF), furfural and diethyl succinate, as well as other compounds, to our knowledge, newly correlated to beer aging.FCT SFRH/BD/31056/200